The present invention relates to improved longitudinal discharge laser electrodes, and more particularly, it relates to improved electrodes for metal vapor lasers.
Longitudinal discharge lasers have a number of uses. Specifically for metal vapor lasers, applications are known in uranium isotope separation using copper vapor and in medical applications using gold vapor. Other metal vapor laser media include lead and borium. An example of the use of copper vapor lasers to pump dye lasers for uranium isotope separation is described in UCRL-88040 on Atomic Vapor Laser Isotope Separation by James I. Davis. This paper describes work done as of the Fall of 1982 with individual copper vapor laser pumped dye laser oscillators run over 1,000 hours in accumulated time. This lifetime test not only illustrates that copper vapor lasers act usefully as dye laser pump sources, but also that copper vapor laser lifetime is an important issue for atomic vapor laser isotope separation. Since the copper vapor lasers had to be stopped several times to replenish the copper supply, the copper vapor laser design employed in the 1000 hour life test differs from the design needed for an isotope separation plant.
In the past, a metal vapor laser electrode was typically a single solid cylinder. In the region between the two electrodes an electrical discharge excites the metal vapor so that it reaches an energy level from which it can lase. Laser light of the appropriate wavelength can traverse this region of excited metal vapor and gain energy through stimulated emission. During the electrical discharge between the two electrodes sputtering takes place from the electrodes. This sputtering from the glow discharge of these prior art electrodes results in a limited electrode lifetime due to wear, a formation of damage centers for hollow cathode discharge to take place leading to further damage, and contamination of wicks if they are being used as the metal vapor source. Weld lines for these solid cylindrical electrodes have also been damage centers.
Past metal vapor laser electrode designs are shown in U.S. Pat. No. 3,654,567 to Hodgson and in U.S. Pat. No. 4,247,830 to Karras, et al. Hodgson's FIG. 1 displays a combined electrode-wick design where each electrode is a single material piece across the bottom of the laser at each end. Hodgson's FIG. 2 shows single-piece prior art cylindrical electrodes completely inside of the tube containing the discharge. Karras, et al.'s FIG. 1 reveals the prior art design where part of the single-piece cylindrical electrode is outside the tube which contains the plasma. In this configuration, the strong discharge electric field passing from outside to inside the tube containing the discharge damages the tube with resulting hollow cathode discharge leading to further damage.